We are "Linear Circuits" an embedded product design and development service company. We have designed a product for one of our customer based on Conneccore 6UL. The product is successfully completed and deployed in field. So far we deployed more than 50 products since last 2 years.

Recently we purchased 5 connect core modules from digikey and soldered on to the target board. Out of 5 there 3 modules functioning as expected and 2 are not working. Following are the modules serial numbers which are not working:
SN:183404054142
SN:183504060993

In one module(183404054142) we are seeing 1V on PWR-IO (We have 100k pull up on this pin as per the design recommendation) pin which is power control pin from MCA. We verified all the pins and components soldered and there shorts. The module is not booting. Is this a known problem or any suggestions for debug?

In the second module(SN:183504060993), the Connectcore constantly restarting from middle of the boot process.